crypto: ecdh - fix big endian bug in ECC library

commit f398243e9fd6a3a059c1ea7b380c40628dbf0c61 upstream.

The elliptic curve arithmetic library used by the EC-DH KPP implementation
assumes big endian byte order, and unconditionally reverses the byte
and word order of multi-limb quantities. On big endian systems, the byte
reordering is not necessary, while the word ordering needs to be retained.

So replace the __swab64() invocation with a call to be64_to_cpu() which
should do the right thing for both little and big endian builds.

Fixes: 3c4b2390 ("crypto: ecdh - Add ECDH software support")
Cc: <stable@vger.kernel.org> # v4.9+
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

crypto/ecc.c

@@ -906,10 +906,11 @@ static void ecc_point_mult(struct ecc_point *result,
 static inline void ecc_swap_digits(const u64 *in, u64 *out,
 				   unsigned int ndigits)
 {
+	const __be64 *src = (__force __be64 *)in;
 	int i;
 
 	for (i = 0; i < ndigits; i++)
-		out[i] = __swab64(in[ndigits - 1 - i]);
+		out[i] = be64_to_cpu(src[ndigits - 1 - i]);
 }
 
 static int __ecc_is_key_valid(const struct ecc_curve *curve,